Biogeography activity

A student with two of his jars of seeds in salt-water. One of his seeds germinated while in the salt-water!

Research assistants with the Darwin Correspondence Project joined the teaching team for a new Freshman Seminar at Harvard College called “Getting to Know Darwin.” The class was composed of first year undergraduates and was taught by Ned Friedman, director of the Arnold Arboretum at Harvard University and Professor in the Department of Organismic and Evolutionary Biology. Here is a link to a feature about the course.

While studying biogeography, the class conducted two experiments that provided first-hand knowledge of Darwin’s work. The first experiment mimicked Darwin’s 1855 work on seeds and salt-water. The experiment is delightfully simple: each student took four jars, filled them with salt water, added one species of seed to each jar, and labelled the jars with the seed type. The students then left the seeds in their jars for four weeks. At the end of these four weeks, the students rinsed off their seeds and planted them in soil with labels to indicate where they had planted each species. Each week the class met, the students were able to check on their seeds to see whether the plants had germinated. The results aligned very well with Charles Darwin’s: those seeds that he had found to sprout also sprouted, while those seeds that didn’t germinate in Darwin’s experiment also failed to germinate in our own time. This experiment is a beautifully simple illustration of biogeography: many seeds survive weeks in salt-water and are still capable of germinating. Darwin saw this experiment as an explanation of the means by which plants appear in disparate locales.

The other experiment the class conducted also investigated the method by which species appear in different geographic locations. To conduct this experiment, each student was given a duck’s foot, string, and had access to a pond. The ducks’ feet were obtained from a local butcher. Each student tied a string around their duck’s foot and dangled it into the pond. The class left the feet in the pond for two hours. After two hours, each student should pull their duck’s foot out of the pond and see if any living creatures have attached to it. This experiment demonstrates the manner in which specimens can be transported by birds across both water and land.